I. Field of the Invention
This invention relates to electromechanical writing devices.
II. Prior Art
Known electromechanical writing devices may have a plurality of connecting bars provided between two outer side plates to form a rigid frame in which a writing head is moved on a carrier so as to traverse past a recording paper and during this movement to perform a writing operation. The writing head may be in the form of a mosaic printer, for example, and be energized by electric signals supplied thereto via a multi-core cable.
General prerequisites for electromechanical writing devices are simplicity of design and ease of maintenance. To this end, the individual components of the writing device, and especially the sensitive writing head, must be easily accessible and yet, on the other hand, the writing device must be compact as a whole. Moreover, it must be possible to carry out any maintenance work required without involving difficult dismantling of components of the writing device.
According to the present invention there is provided an electromechanical writing device comprising a writing head, carrier means for carrying the writing head, guide means along which the carrier means is movable during a writing operation, a writing platen disposed parallel to the direction of movement of the carrier means, an upper frame part on which the guide means is mounted, a lower frame part, a pivot axis about which the upper frame part and the lower frame part are mounted for pivotal movement relative to one another, the pivot axis being disposed parallel to the length of the writing platen which is disposed in a plane which bisects an imaginary cylinder coaxial with the pivot axis, an adjustable stop means for adjusting the distance between the writing head and the writing platen and the position of closest approach of the upper frame part and the lower frame part.
This construction makes it possible to build an electromechanical writing device in a very simple manner and yet, at the same time, to increase the precision of adjustment of the distance between the writing head and the writing platen.
The pivot axis may constitute a cross bar forming part of the upper frame part, the cross bar being disposed in recesses in the lower frame part. This makes it possible to remove the upper frame part and the lower frame part, during or after the pivotal movement of the upper frame part relative to the lower frame part, so that the writing device is then in two halves, each being perfectly accessible, for example, for maintenance.
Preferably each said recess has a depth which is at least twice the diameter of the cross bar, the longitudinal sides of each recess being disposed parallel to the said plane which bisects said imaginary cylinder. This ensures that the cross bar can only be removed from the recesses in a predetermined position of the upper frame part relative to the lower frame part so that the upper frame part is removed from the lower frame part in a direction in which damage to sensitive components, such as the writing head, is reduced or prevented.
The cross bar may be provided with sleeve elements, each of which has a flat surface, one sleeve element being disposed partially in each recess, retaining means being provided on a lower frame part for engaging the sleeve elements and preventing removal of the cross bar from the recesses, the arrangement being such that, when the upper frame part and the lower frame part are in a predetermined relative position, the flat surfaces of the sleeve elements are so disposed relative to the retaining means that the cross bar may be removed from the recesses.
The writing device preferably includes a locking mechanism for preventing pivotal movement of the upper frame part and the lower frame part relative to one another, and release means for releasing the locking mechanism to permit said pivotal movement of the upper frame part relative to the lower frame part. The locking mechanism may comprise a lever which is pivotally mounted on the upper frame part and is provided with a jaw which engages in abutment on the lower frame part to prevent said pivotal movement of the upper frame part relative to the lower frame part.
Said lever may carry a locking pin which is urged by spring means into a bore in the upper frame part and which is moved out of the bore to allow the upper frame part to pivot relative to the lower frame part by the release means which are mounted on the carrier means. A resilient stop mechanism may be disposed on the upper frame part for determining a rest position of the carrier means, movement of the carrier means against the action of the resilient stop mechanism causing the release means to release the locking mechanism.